DISTRIBUTION OF SPORES 113 



merely taken into the body of the insect and passes unharmed 

 through the alimentary tract, or is regurgitated or accidentally ad- 

 heres at the surface, or is mechanically transferred to the host 

 plant. The relation of insects to disease in plants is therefore less 

 spectacular than in animals but is none the less quite as important. 



Rand and Pierce (1920) are among the first to bring together 

 from widely scattered sources the information extant on insects as 

 agents in the transmission of fungi. The later accounts of Rand, 

 Ball, Caesar, and Gardner (1922) and the comprehensive works 

 of Leach (1935, 1940) describe the present status of this topic. In 

 the appendix to the volume by Leach (1940) is a long list of in- 

 sect-transmitted fungi. 



Abundant evidence is at hand to show that the brown-rot fungus 

 of stone fruits, Sclerotinia fructicola, is transported by bees, wasps, 

 May beetles, and squash bugs at the season when the fruit is ripen- 

 ing. Heald [Arthur (1929)] demonstrated that mites are carriers 

 of Sporotrichum anthophihim, the cause of bud rot of carnations. 

 Punctures made by the cabbage maggot, Pegomya brassicae, af- 

 ford portals of entry for Phoma oleracea, the cause of cabbage 

 blackleg. The woolly aphis, Schizoneura lanigera, is associated 

 with the spread of the apple-canker fungus, Nectria ditissima. 

 Similarly Ehrlich (1934) showed that N. coccinea infects beech, 

 but only if the bark is infested with Cryptococcus fagi. Initial 

 infection is possible provided that the living tissues of the bark 

 have been injured by the insect while feeding. The fungus then 

 grows parasitically and kills the beeches within 2 or 3 years. 



Certain species of Orthoptera, Lepidoptera, Coleoptera, and 

 Hemiptera were found by Wolf (1916) to distribute Cercospora 

 personata on peanuts. Among these orders grasshoppers, because 

 of their powers of flight, were regarded as especially important 

 vectors of this peanut-leaf-spot fungus. A single longicorn 

 beetle, Leptostyhis maculata, was found to transport 320,000 

 spores of Endothia parasitica and, according to Studhalter and 

 Ruggles (1915), 19 other insect species also act as carriers of this 

 fungus. 



The larval forms of many species find rust spores to be suitable 

 food, and they effectively aid in distributing them. Arthur (1929) 

 records that the larvae of Smyrithurus sp., a neuropterous insect, 

 carries Puccinia rubigo-vera iritici, and the larvae of Diplosis sp., 



